Electrical discharge device



c. SPAETH 1,908,649

ELECTRICAL DISCHARGE DEVICE May 9, 1933.

2 Sheets-Sheet 1 Filed March 2, 1929 GHeaues 5FRTH INVENTOR ATTORNEY May 9, 1933.

c. SPAETH 1,908,649

ELECTRICAL DISCHARGE DEVICE Filed March 2, 1929 2 Sheets-Sheet 2 AALAA GHARLES PRTH INVENTOR ATTORNEY Patented May 9, 1933 UNITED STATES PATENT, OFFICE CHARLES SPAIETH, OF FLUSHIhTG, NEW YORK ELECTRICAL DISCHARGE DEVICE Application filed March 2,

provide an electrical discharge tube which is capable of producing a .very eflicient white light. v I

Another object is to provide an electrical discharge illuminating tube wherein the color characteristics of the emitted light may readily be modified in a predetermined manner. e

A further object is the provision of an I electrical discharge tube operating at high efliciency and adapted to produce a concentrated brilliant light emission approximating sunlight. v

In accordance with my invention a radiant energy emitting discharge device is constructed having a fillinglof gas at reduced pressureand a plurality of electrodes for conducting an electrical discharge therethrough. For modifying the light emission from the device auxiliary means are ar- 5 ranged to add to the gas filling in the desired amounts an agent for modifying'the radia tion spectrum. This auxiliary device is preferably in the form of a mercury reservoir provided with means for Iiberatingmercury vapor. In place of mercury other elements 'or combinations of elements may be used, for example, cadmium, thallium, sodium or cal-' cium, depending on the spectrum modification desired. Y

A preferred form of my invention for illuminating purposes comprises an envelope containing an atmosphere of rare gas such as neon and having a reservoir of mercury. Electrodes are provided for passing a discharge directly through the rare gas and another electrode for causing a discharge to be passed to themercury in order to vaporize it.

In order to secure the desired characteristics of illumination from the device means, such as resistances, inductances or capacitances are provided for controlling the relative intensities of the discharges. For liberating the mercury suitable heating means may be employed in place of the auxiliary electrode.

This heating means may comprise any suitused up and hence the color of 1929. Serial a... 848,873.

able source of external heat, but preferably is in the form of a heating coil placed adjacent to the mercury reservoir'and adapted to be energized by the discharge current.

When it is desired to secure a White light 55" approximatingthat of sunlight the filling of the envelope may be of neon gas used in conjunction with a reservoir or other means for supplying an exactly proportioned amount of mercury vapor. It is advisable where the tube is to be operated over a relatively long period of time to maintain the mercury vaporizing means in operation at the correctintensity during the entire operation of the device. It is, however, possible to start the discharge through the rear gas column and then supply the necessary quantity of mercury vapor for a short period of time, after which the device will continue to emit a white light for some time. As 7 operation is continued the mercurycleaned up, apparently either by condensation, occlusion, absorption or some other phenomena and the light emitted by the device gradually reverts to the characteristic color of. the rare gas, which in the case of neonis substantially red. By operating the mercury vaporizing device at the correct intensity mercury vapor is supplied at the same rate at which it is the emitted 30 light remains constant. Y I

For. produegg other colors of light other monatomic ga for example, helium, argon, xenon, crypton, m'ay be used with mercury vapor, or one of a mixture of the rare gases of a given characteristic color emission may be used in conjunction with means for liberating a gas or metallic vapor having another color characteristic. 3

- device constructed in accordance with my invention may-also serve as a generator of oscillations of extremely high frequency and constancy.

- Other objects and advantages and the manner of obtaining them will be made clear the following specification and accompanying drawings.

In the drawings, Fig. 1 shows a device con structed in accordance with my invention wherein the modification of the emitted spectrum is obtained by the passage of a dis charge to a spectrum modifying material.

Fig. 2 shows a somewhat similar device wherein the light modifying material is activated by a heating device.

Fig. 3 shows an alternating current tube utilizing an alkaline metal cathode.

Fig. 4 shows a device similar to that shownis illustrated.

Fig. 8 shows an oscillator constructed in accordance with my invention.

Referring more particularly to the drawings, Fig. 1 illustrates an electrical discharge tube comprising a light transmitting envelope 1 filled with rare gas, such as neon, and having a pair of main discharge electrodes 2 and 3 of any well known type, having the usual lead-in wires. The pressure of the gaseous atmosphere may range anywhere from .1 to 50 millimeters but I find it preferable to use a pressure in the neighborhood of 6 millimeters. A reservoir for a quantity of mercury 4 is provided in the form of an a pendix' 5. For energizing the tube the main electrodes 2 and 3 are connected across a suitable source of current 14 by means of conductors 6 and 7. The source 13 may be of either direct or alternating current of a suitably high potential. Connected in series .with the conductor 6 is an adjustable resistance 8. For causing discharge to pass to the mercury 4 a connection 9 is made between a lead-in wire 59 sealed through the wall of the reservoir 5 and making contact with the mercury, and the conductor 6. In series with the conductor 9 is an adjustable resistance 10.

In operation a current is caused to pass from the source .13 between the two electrodes 2 and 3 thereby energizing the filling of rare gas and causing it to emit light having certain color characteristics. For example, where the rare gas is neon the light will be predominantly red. In order to modify these color characteristics the resistance 10 is adjusted so that a discharge passes between the electrode 3 and mercury 4, thereby causing a quantity of the mercury to be vaporized. The mercury vapor diffuses through the gas in the envelope 1, emitting light rays of its characteristic blue color. By properly adjusting the resistance 10 it is possible so to balance the blue rays emitted against the characteristic color of the rare gas as to produce a light emission of any desired color. For example, where the rare gas is neon a proper adjustment of the resistance 10 may be made-to cause the emission of white light,

the blue rays of the mercury being complementary to the red rays of the neon. The resistances 8 and 10 serve also to ballast resistances for balancing thenegative resistance of the gaseous discharge path. These resistances should therefore never be cut entirely out of circuit as the discharge current would increase to an excessive value. While the mercury reservoir is illustrated as positioned near to one of the main electrodes it need'not necessarily be so located. The device will likewise be operative with the reservoir at other positions. By placing the reservoir as shown the impedance of its discharge path is made relatively large.

The device shown in Fig. 2 is the same as that shown in Fig. 1 except that mercury vapor is produced by heating coil 11 instead of by passage of a discharge to the mercury. This tube is operated in substantially the same manner as that of Fig. 1, the only difference beingthat the amount of mercury vapor generated is controlled by varying the amount of heat nerated by the coil 11. This may be done b y adjusting the resistance 12 v Fig. 3 shows a tube adapted for operation by alternating current. Current is supplied by means of a' transformer 14 energized from a line 15. A connection 22 is made from a center tap 16'of the transformer to an alkaline metal electrode 17 of the tube.

This connection includes in series an inductance 23 which functions to prevent flicking of light in the usual well known manner,

when the device is used on low frequency alternating currents. The two main terminals of the secondary of the transformer are connected to two ordinary metallic electrodes 18 and 19 at opposite ends of the tube through resistances 20 and 21 respectively. As the electrodes 18 and 19 are comparatively small in relation to the electrode 17 a rectifying action occurs, the discharge passing alter- -nately between electrodes 17 and 18 and 17 The operating area of the alkaline metal cathode should be so proportioned with respect to the discharge current that the current density will be'of but moderate intensity, for example, 3 amperesper square inch or less so that large amounts of metallic vapor will not penetrate the main discharge path and mask the spectrum thereof.

Where one or several of these metals is is connected to the tube envelope.

used in place of mercury for light modifica- While the path between the two electrodes 18 and 19 is relatively short the amount of leakage current passing between these two electrodes will be small, as the cathode fall of potential of an ordinary electrode made of aluminum, iron or other similar material is 1in the'neighborhood of several hundred vo ts.

For liberating mercury vapor into the gaseous atmosphere an auxiliary circuit comprising a reservoir 23 containing mercury 24 A leadin wire 25 passes through the wall of the reservoir into contact with the mercury. For causing the discharge to pass to the mercury an auxiliary connection 26 is made between the lead-in wire and one side of the secondary of the transformer 14. This connection 26 includes in series an adjustable resistance 27 by means of which the amount of mercury vapor liberated may be controlled in the same manner as that set forth in connection with Fi 1. For preventing the alkaline utilized for one of the electrodes the tube envelope should be made of some alkaline metal resistant glass such as Pyrex or other borosilicate glass. By utilizing such a glass it is also possible to operate at high temperatures without danger of collapse of the tube walls. Where no alkaline metal is used it is, of course, possible to make the tube envelope of any ordinary type of glass provided the intensity of the discharge is not sufficie nt to heat the glass to the softening point.

The device shown in Fig. 4 is substantially the same as that shown in Fig. 1 except that it is especially adapted to operate on low voltage direct current from a source 37. The

' cathode 31 is of the alkaline metal type simi-' lar to electrode 17 of Fig. 3'. The anode 32 may be of any well known type but preferably comprises a thin walled cylinder of nickel or iron which is so proportioned as to be heated red hot by the passage of normal discharge current through the tube. heated nickel anode has a fall of potential of but approximately 10 volts. The entiredevice may therefore be operated on the ordinary commercial lighting voltageof 110 to 120 volts direct current.

be of relatively The' Fig. 5 shows a tube similar to that of Fig.

4 with the exception that instead of an alkaline metal cathode an indirectly heated oxide f coated cathode ,of well known construction may be used. I find that a suitable electrode may comprise a thin cylinder 33 of nickel coated with an oxide of barium, strontium or calcium. 1

' This cylinder may be heated by a resistance coil 34 energized by a" heating transformer 35, the secondary of which is rovided with I an adjustable tap 36 by whic theneutral point may be determined.

Fig. 6 shows a device similar to that of Fig. 4 with the exce tion that a heating coil 38 is provided for iberating the necessar amount of mercury vapor. This heating c011 is the same as that shown in Fi 2 and may be similarly controlled by a suitable resistance 39.

Fig. 7 illustrates a lamp adapted for television pur oses, the lamp comprising a gas filled enve ope 40 having a pair of plate elecv trodes 41 and 42 spaced apart a distanceless than the mean free path of the gas in the well known manner. The envelope is filled with an atmosphere of inert gas, for example,

neon and a reservoir 43 containing mercury is provided. In operation a white light is obtained in the same manner as set forth in connection with Fig. 1. The discharge cannot pass directly between the two plates because of their close spacin passes around to the outsi e faces of the plates illuminating them in the well known manner.

Fig. 8 shows a device constructed in accordance with myinvention arranged to produce oscillations of any desired frequency.

As shown in this figure a discharge device is used comprising an envelope 44 filledwith rare gas and provided with an alkaline metalcathode 45 and an anode 46. Theanode may be of any ordinary well known type or may nickel or comprise a thin walled cylinder 0 iron, as disclosed in connection with Fig. 4. This electrode is proportioned so asto be heated red hot by the passage of normal discharge current through the tube. For causing a discharge between'these electrodes a source of current 47 is provided. Electrodes 45, 46 are connected with the source 47 by means of conductors 48 and 49 respectively.

In series with the conductor 49 an adjustab e resistance 50 is connected. An auxiliary mercury electrode 51 is connected to the envelope 44 and for energizing this electrode a connection 52 including in series an adjustable resistance 53. is made to the source 47. In order to control the frequency of the generated oscillations a tuned circuit comprising an inductance 54 and a condenser 55 is connected between the electrodes 45 and 46.

and therefore.

By varying the capacity of the condenser 55 generated oscillations. The oscillations may be utilized in any desired manner by coupling to the inductance 54 a work circuit 56. Oscillations of a difierent frequency maybe obtained by connecting between the electrodes 45 and 51 another tuned circuit 57 which may supply a work circuit 58. Extremely short wavelength oscillations may be obtained by connecting a suitable work circuit directly across the electrodes 45 and- 46 without any auxiliary tuning devices. For.

example, a tube containing neon gas and having a-length of 18 inches will produce oscillations having a wavelength in the neighborhood of one meter.- The oscillations produced by this type ofgenerator are of extremely constant wavelength and amplitude.

It is well known that ordinary light tubes utilizing a filling of rare gas are adapted to operate at only relatively low current densities and that in order to secure life long enough for commercial purposes it has been thought necessary to utilize electrodes operating at relatively low current densities. A device constructed in accordance with my invention will, on the contrary, operate at extremely high current densities without ex cessive heating and without excessive deterioration. For example, by utilizing an alkaline metal cathodeand hot anode, I am able to pass through a tube 18 inches long and 1 inch in diameter a. discharge of 6 amperes under pressure of 220 volts. Even whenoperating at this relatively highcurrent density the life of the tube is from 3,000 to 7,000 hours.

Where neon gas and an auxiliary mercury electrode are used, as set forth, the color may be adjusted from the characteristic neon color, through white, to the characteristic mercury color. The efliciency of tubes constructed in accordance with my invention is extremely high. For example, when using neon gas with mercury vapor to produce a white light the amount of energy consumed is only about 0.20 watt per spherical candlepower. Be-

where a white, silent and relatively cool, high I intensity illuminating source is desired, asin the recording of synchronized sound pictures.

Any oscillations which are inherently generated.are of such short wave length as not to interferewith ordinary amplifying systems. It will'be obvious to those skilled in the art that the invention is capable of a wide variety of modification and adaptation and that the present disclosure is intended merely to illustrate its nature without limiting its scope which is set forth in the appended claims.

-.for passing a discharge through said gas,.a

mercury reservoir attached to said container,

means for vaporizing a quantity of said mercury, and an output circuit for high frequency oscillations connected between two of said electrodes.

' 2. A device in accordance with claim 1 wherein the output circuit comprises an inductance and a variable condenser.

3. In an oscillator, an envelope containing a filling of gas, a plurality of electrodes for passing a discharge through said gas, a reservoir containing a light color modifying substance attached to said container, means for vaporizing a quantity of said substance, and an output circuit for high frequency oscillations connected between two of said electrodes.

In testimony whereof, I have-signed my name to this specification this 28th day of 

